Decomposition Stages and Carrion Insect Succession on Dressed Hanging Pig Carcasses in Nan Province, Northern Thailand

Abstract

The principal colonizing insect species and their succession pattern on six dressed, hanging pig carcasses (Sus scrofa domestica) in Nan province, Northern Thailand, was evaluated along with the cadaver decomposition stages in the monsoon wet, winter and summer seasons during May 2010 – August 2011 at two different habitat types, mixed deciduous forest and suburban plantation area. At each site, a dressed pig carcass was suspended by its neck from a tree branch 1.2 m of pig’s feet above the ground. Carcasses were protected from carnivorous vertebrates, but not the ambient weather (wind, rain or sunlight), by ground fencing (enclosure). The ambient and internal carcass temperature, relative humidity, insect succession and rate of carcass decomposition were monitored in both habitats. From this preliminary study, 43–45 and 39–40 different cadaver-associated (nonaccidental) taxa were collected in the mixed deciduous forest and suburban plantation area, respectively. The observed insect succession pattern broadly conformed to those reported from other (mostly temperate) regions. The primary and dominant necrophagous colonizers were the calliphorid dipterans, Chrysomya megacephala (F.) and Achoetandrus rufifacies (Macquart), in both habitats. Unconfirmed (insufficient sample sizes) trends of interest for further confirmation included that: (i) the decomposition rate was potentially faster in the monsoon wet and summer seasons in both habitats than in winter; and (ii) that whilst the patterns of insect secession occurred in a predictable sequence, they varied in timing and species composition between the habitats.